diff --git a/changelog/unreleased/SOLR-18552-mmap-arena-permits.yml b/changelog/unreleased/SOLR-18552-mmap-arena-permits.yml
new file mode 100644
index 000000000000..2b76f2253732
--- /dev/null
+++ b/changelog/unreleased/SOLR-18552-mmap-arena-permits.yml
@@ -0,0 +1,7 @@
+title: Set a lower shared arena permit limit for MMapDirectory
+type: changed
+authors:
+  - name: Nick Shanin
+links:
+  - name: SOLR-18552
+    url: https://issues.apache.org/jira/browse/SOLR-18552
diff --git a/solr/bin/solr b/solr/bin/solr
index 247e76c85907..e732c63d63e8 100755
--- a/solr/bin/solr
+++ b/solr/bin/solr
@@ -722,7 +722,8 @@ fi
 FG="false"
 FORCE=false
 SOLR_OPTS=(${SOLR_OPTS:-})
-SCRIPT_SOLR_OPTS=()
+# Use the lower shared arena permit limit recommended for Lucene 9.
+SCRIPT_SOLR_OPTS=("-Dorg.apache.lucene.store.MMapDirectory.sharedArenaMaxPermits=64")
 PASS_TO_RUN_EXAMPLE=()
 
 if [ $# -gt 0 ]; then
diff --git a/solr/bin/solr.cmd b/solr/bin/solr.cmd
index ac67559faa53..a7cb4d3404d9 100755
--- a/solr/bin/solr.cmd
+++ b/solr/bin/solr.cmd
@@ -789,7 +789,8 @@ IF NOT "%SOLR_HOST%"=="" (
   set SOLR_HOST_ARG=
 )
 
-set SCRIPT_SOLR_OPTS=
+REM Use the lower shared arena permit limit recommended for Lucene 9.
+set "SCRIPT_SOLR_OPTS=-Dorg.apache.lucene.store.MMapDirectory.sharedArenaMaxPermits=64"
 
 REM Default placement plugin
 IF DEFINED SOLR_PLACEMENTPLUGIN_DEFAULT (